The objective of this research is to gain a better understanding of the pulmonary circulation in man, in health and disease. As we have become increasingly aware of the importance of the lung vasculature in a variety of diseases we have also realized the need for more precise methods of studying the pulmonary circulation. Previous work has shown the necessity of considering the pulsatile quality of blood pressure and flow in order to include the effects of blood inertia and vascular compliance as well as vascular resistance. Therefore, it is planned to use techniques of biomathematics and bioengineering to assess pulmonary hemodynamics in patients with heart disease. We propose to measure vascular impedance, power dissipation, energy cost of transport, effective pulmonary vascular resistance, auto and cross correlation, and power spectral density functions of the pulmonary vasculature in selected patients undergoing thoracotomy. These measurements will be related to the internal efficiency of the heart thereby giving a more complete picture of the pulmonary circulation. Mathematic models of the pulmonary circulation developed in this laboratory will be tested under various clinical and experimental conditions. Also, it is anticipated that a model including the right heart can be developed, and, after experimental validation, used in the clinical evaluation of patients.